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DES decryption

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  • 25-03-2008 9:50pm
    #1
    AARRRGH
    Closed Accounts Posts: 12,382 ✭✭✭✭


    Hello

    I've implemented DES encryption in C. Now I want to implement decryption :)

    I've read:

    Decryption is simply the inverse of encryption, following the same steps as encryption, but reversing the order in which the subkeys are applied.

    Does this mean reverse the order of the subkeys when XORing the output of the e-bit selection table? Or does it mean something else?

    Any help appreciated.

    Thanks


Comments

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    #2
    AARRRGH
    Closed Accounts Posts: 12,382 ✭✭✭✭AARRRGH


    Yep, that's it, just got it working!

    Yay.


  • Options
    #3
    Sherifu
    Registered Users Posts: 17,727 ✭✭✭✭Sherifu


    You need to give people more time to answer :pac:


  • Options
    #4
    AARRRGH
    Closed Accounts Posts: 12,382 ✭✭✭✭AARRRGH


    I'm a machine!

    You can still answer if you want, I don't mind ;)


  • Options
    #5
    DublinDilbert
    Registered Users Posts: 5,370 ✭✭✭DublinDilbert


    dublindude wrote: »
    Hello

    I've implemented DES encryption in C. Now I want to implement decryption :)

    I've read:

    Decryption is simply the inverse of encryption, following the same steps as encryption, but reversing the order in which the subkeys are applied.

    Does this mean reverse the order of the subkeys when XORing the output of the e-bit selection table? Or does it mean something else?

    Any help appreciated.

    Thanks

    It means for decryption the round keys are calculated exactly the same way as encryption... except they are applied in reverse order to the rounds in the encryption process, to perform decryption....


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